Polytetrafluoroethylene dispersions



United States Patent 3,352,811 POLYTETRAFLUOROETHYLENE DISPERSIONS Mille Stand, 500 E. 83rd St., New York, N.Y. 10028 No Drawing. Filed Jan. 23, 1967, Ser. No. 610,754

3 Claims. (Cl. 260-31.2)

ABSTRACT OF THE DISCLOSURE P-olytetrafluoroethylene powder is mixed with a combination of solvents to form a dispersion which can be sprayed under pressure from an aerosol can. The combination of solvents may include one of the low boiling point ketones, a polymeric perhalogenated carboxylic acid, and trichlorotrifluoro acetone. Other liquids may be used, such as, trichloroethylene and polymeric trifluorovinylchloride.

This invention relates to fluid compositions in the form of dispersions of polytetrafluoroethylene, sold under the trademark Teflon, in a liquid medium and has particular reference to fluid dispersions which can be packaged in aerosol dispensers under pressure. The fluids can be sprayed onto metal surfaces to act as lubricants or protective coatings.

This application is a continuation-impart of my copending application, 540,831, filed Apr. 7, 1966, for Polytetrafluoroethylene Dispersions. This parent application describes and claims dispersions which employ certain oxygen-containing polyfluoro-organic compounds such as mono-chlorodifluoro-acetic acid, trichlorotrifluoro-acetone and dichlorotetrafluoroacetone in conjunction with the other organic solvents. These compounds gave satisfactory results and produced fluids containing a high percentage of polytetrafluoroethylene in apparent solution.

Difficulties developed when the above described fluids were packaged in aerosol containers because the powerful solvent action of the above named solvents on the valve and stem parts of the aerosol dispensers. These difliculties could be overcome only by substituting a new and very expensive valve and stem structure for the valve and stem generally used in such dispensers. Because of this, commercial marketing of these dispersions is not economical.

It has been found that polymeric perhalogenated derivatives of some alkanes can reduce the need for the oxygen containing compounds as named above to one percent of the total fluid. One class of such solvents includes polymeric trifluorovinyl chloride and their car- 'boxylic acid derivatives. The alcohol derivatives of this solvent can also be used. In some cases the oxygen containing compounds can be eliminated entirely and the result is a satisfactory dispersion with improved lubricating qualities imparted to the resultant Teflon coating.

The liquid medium may include other organic liquids which set as a diluent for the fluoro-organic compound. These diluents can be chemically inert to the fluoroorganic compound and are added to produce the fluidity necessary to produce a fine spray mist when discharged through a small orifice of an aerosol can. The diluent must be sufficiently volatile to evaporate rapidly and leave no residue at a temperature well below the sintering temperature of polytetrafluoroethylene. Examples of liquid organic compounds which may be used as diluents are the chlorinated hydrocarbons, for example, trichloroethylene, carbon tetrachloride, and hexachloroethane. Ketones may also be used as diluents such as methylethyl ketone or methyl isobutyl ketone. Also, some nitro alkanes may "be used, such as Z-nitro propane, dimethylformamide, or tetrahydrofuran.

The dispersion may have a polytetrafluoroethylene content from 5 to 17 percent and the Teflon particles may have a size within the range of 10 to 1,000 microns, preferably with an average size of 200 to 500 microns.

If the surface is a metal surface or a heat resistance surface such as a ceramic, the liquid in the sprayed coating is allowed to evaporate and then the Teflon may be sintered.

One of the objects of this invention is to provide an improved polytetrafluoroethylene dispersion which avoids one or more of the disadvantages and limitations of prior art dispersions.

Another object of the invention is to permit packaging the dispersion in the same type of aerosol pressure container as is used to package other spray mixtures.

Another object of the invention is to reduce the cost of Teflon dispersions.

Another object of the invention is to increase the percentage of Teflon in the dispersion.

The following is a description by way of example of methods of carrying out the present invention.

Example 1 Example 2 The following composition was prepared:

Grams Teflon powder 15 Specific gravity from 2.1 to 2.3. (The average particle size was 500 microns; the maximum size was 1,000 microns.)

Polymeric trifluorovinylchloride (CF --CFCl) (where x lies within the range of 7 to 11) having a density of 1.95 to 1.97 and a viscosity of to 650 centipoises, measured at F.

Trichloroethylene 84.3.4

Both the above compositions were packaged in aerosol dispensers and used to apply Teflon films to various objects. In some cases, the Teflon film was used to reduce friction. In other cases the Teflon film was used as a protective coating.

Both the above compositions formed a fine spray when applied with a conventional aerosol spray device. There was no clogging of the aperture and after continued use the material forming the nozzle showed no sign of wear or disintegration.

While there have been described herein what are at present considered preferred embodiments of the invention, it will be obvious to those skilled in the art that many modifications and changes may be made therein without departing from the essence of the invention. It is therefore to be understood that the exemplary embodiments are illustrative and not restrictive of the invention, the scope of which is defined in the appended claims, and that all modifications that come within the meaning and range of equivalency of the claims are intended to be included therein.

The embodiments of the invention in which an exelusive property or privilege is claimed are defined as follows:

P, g; 1. A fluid composition in the form of a dispersion of from 5 to 18% polytet'rafluoroethylene in a liquid (2-) *trichlorotrifluoroacetone of 0.75% to"4.0% by (3) the remainder a methyl ketone havingv a boiling point less than- 102 degrees, centigrade.

2. A fluid composition in the form of a dispersion of from 5 to 18% of polytetrafluoroethylene in a liquid medium, which medium consists essentially of a mixture of (1) polymeric trifluorovinylchloride of'0.5 to 3.0 by

weight, having the general formula: (CF CFCD (where x has an integer value within the range of 7 to 11) having a density of 1.95 to 1.97, and,

(2) the remainder trichloroethylene.

3. A fluid composition as claimed in claim 1 wherein the methyl ketone is selected from the group consisting of dimethyl ketone, methyl ethyl ketone, methyl propyl ketone, and methyl isopropyl ketone.

References Cited UNITED STATES PATENTS 3,260,693 7/1966 Stand 26032.8 2,863,844 12/1958" Fuchs 260--30.2 2,656,332 10/1953 Sprung 260-31.2. 2,876,206 3/1959 Roselle 26O31.2

JULIUS FROME, Primary Examiner. 

1. A FLUID COMPOSITION IN THE FORM OF A DISPERSION OF FROM 5 TO 18% POLYTETRAFLUOROETHYLENE IN A LIQUID MEDIUM, WHICH MEDIUM CONSISTS ESSENTIALLY OF A MIXTURE OF (1) POLYMERIC PERHALOGENATED CARBOXYLIC ACID OF 0.5% TO 3.0% BY WEIGHT HAVING THE GENERAL FORMULA: CL(CF2CFCL)XCF2COOH (WHERE X HAS AN INTEGER VALUE WITHIN THE RANGE OF 5 TO 8) (2) TRICHLOROTRIFLUOROACETONE OF 0.75% TO 4.0% BY WEIGHT CCL2F-CO-CCLF2, AND (3) THE REMAINDER A METHYL KETONE HAVING A BOILING POINT LESS THAN 102 DEGREES CENTIGRADE. 